Played all 4 and I must say they were definitely very entertaining scenarios. In terms of difficulty I'd rank them as:

PART I: 7/10 managed a marginal victory
PART II: 9/10 managed a draw, both sides had more than 10k loss of points
PART III: 3/10 managed a marginal victory, almost a decisive
PARTIV: 5/10 same as above

As you can see, I found the scenarios that you have the Spanish side the most challenging. The reason for that is lack of any decent armor, most of your tanks are M60s with 1 or 2 Leo2A4 platoons and you have to attack prepared French positions with tanks, including Lecrerc's. Scenario III was by far the easiest, you can just rush to occupy any hexes not occupied by the Spanish and then defend them. IV was a little more challenging, but if you were methodical and use your light armor correctly, you can make it. The biggest asset in both of them are the Leclerc tanks, maybe if you gave the French side mainly AMX30s it would be harder.

Played all 4 and I must say they were definitely very entertaining scenarios. In terms of difficulty I'd rank them as:

PART I: 7/10 managed a marginal victory
PART II: 9/10 managed a draw, both sides had more than 10k loss of points
PART III: 3/10 managed a marginal victory, almost a decisive
PARTIV: 5/10 same as above

As you can see, I found the scenarios that you have the Spanish side the most challenging. The reason for that is lack of any decent armor, most of your tanks are M60s with 1 or 2 Leo2A4 platoons and you have to attack prepared French positions with tanks, including Lecrerc's. Scenario III was by far the easiest, you can just rush to occupy any hexes not occupied by the Spanish and then defend them. IV was a little more challenging, but if you were methodical and use your light armor correctly, you can make it. The biggest asset in both of them are the Leclerc tanks, maybe if you gave the French side mainly AMX30s it would be harder.

While the Catalan front battles come to a halt with both sides on a defensive stance, the war spills to the Basque region as Spain retaliates to French Air Strikes in the area by mobilizing nearby stationed units across the border. Portugal joins the Spanish side rushing units to the Basque region. A mixed unit of Light Infantry supported by armor encounters very well equipped french regulars delaying their advance near Ascain.

I lost 187 men and 10 armoured vehicles to French 331 men, 2 mortars, 2 VBLs and 20 other armoured vehicles.

Nice scenario, I enjoyed it, however it wasn't particularly hard as long as you watch for the losses. French defence is planned rather badly, its easy to cut and encircle defence pockets as they are not being supported at all. Only think that saved French from decisive defeat was one Armoured section in a place I did not expect (I am not spoiling), that knocked out 2 tanks and 1 Escorpion.

Lost 109 men to Portuguese 199, 11 VABs and other 12 tank-like vehicles. Portuguese lost 11 and 12, respectively. All flags taken by last turn, score 7687:2039.

Really interesting scenario, I was surprised Portuguese can stand such stiff defence. Situation was unclear for first 10-12 turns and I thought I may fail to do it on time. However, unusually to your scenarios, I felt unnecessary pressure with just 22 turns to play it. Yours scens require careful approach and scouting and I had no issues with it before.
What I then recommend is to rise the amount of turns at least to 27.

Lost 109 men to Portuguese 199, 11 VABs and other 12 tank-like vehicles. Portuguese lost 11 and 12, respectively. All flags taken by last turn, score 7687:2039.

Really interesting scenario, I was surprised Portuguese can stand such stiff defence. Situation was unclear for first 10-12 turns and I thought I may fail to do it on time. However, unusually to your scenarios, I felt unnecessary pressure with just 22 turns to play it. Yours scens require careful approach and scouting and I had no issues with it before.
What I then recommend is to rise the amount of turns at least to 27.

Thank you SaSTrooP for your positive feedback, i'm glad you enjoyed the scenarios. Scenario design is very much rewarding for me as it is SP or PBEM gameplay. I kept the turns to 22 on Part VI to precisely add the "pressure" effect on the french commander and with the limited info on the briefing it all adds to the fog of war aspect.

Really enjoyed Part V and Part VI, especially liked the little surprises in Part V ,just a couple of suggestions for amendments :-In Part V hex 59,5 is shallow water, whereas the graphic indicates it should be a bridge. In Part VI hex 67,39 is a ford, again the graphic suggests a bridge. Once again most interesting scenarios, many thanks.

It was fixed on Dec 10 2017 and it is in the patch. Scenhack does not report there is a problem with it though on close inspection, it looks like all your moving units around has created a situation where even Scenhack is confused which is why I normally avoid third-party OOB "fixes".

At some point I will look into this as it looks like it will need to be rebuilt unit by unit manually